Lower Core Body Temperature Research Articles

Effects of Fish Oil with Heat Treatment on Obesity, Inflammation, and Gut Microbiota in Ovariectomized Mice

Background/Objectives: Menopause induces substantial metabolic changes, including a reduction in metabolic rate and an elevated risk of developing metabolic diseases. Fish oil (FO) supplementation has been shown to ameliorate menopause-associated metabolic risks. Hyperthermia treatment (HT) has recently gained attention for its potential to improve metabolic and immune health. However, it remains to be determined whether HT can confer metabolic benefits comparable to those of FO supplementation or enhance the metabolic benefits of FO supplementation. This study aims to delineate the distinctive and collaborative effects of HT and FO supplementation in mitigating menopause-associated metabolic dysfunction. Methods: Female C57BL/6 ovariectomized (OVX) mice were randomly assigned to four groups (n = 12/group) to evaluate the individual and combined effects of FO supplementation (5% w/w) and HT treatment. For HT, whole-body heat exposure was conducted at 40–41 °C for 30 min, 5 days per week. After 12 weeks, animals were used to evaluate the changes in glucose and lipid metabolism, obesity outcome, and inflammatory markers. The gut microbiome analysis was conducted from cecal content by 16S rRNA sequencing. Acute inflammation was induced by lipopolysaccharide (LPS) injection to evaluate inflammatory responses. Results: HT alone distinctively reduced weight gain, lowered core body temperature, and attenuated insulin resistance comparable to FO supplement in OVX mice. The collaborative effect of FO and HT was not evident in metabolic parameters but more prominent in attenuating proinflammatory responses and microbiota modulation. Conclusions: Our findings suggest that the combined treatment of FO supplementation and HT may serve as an effective strategy to mitigate menopause-associated immune susceptibility and metabolic dysfunction. These benefits are likely mediated, at least in part, through the reduction in inflammation and modulation of the gut microbiota.

Does body cooling facilitated by bedding compared to control condition improve sleep among adults (18-64 years old)? A systematic review and meta-analysis.

The relationship between blood distribution, body temperature, and sleep/wakefulness states is still unclear. The aim of the present study is to systematically review the potential beneficial effects of bedding strategies (e.g., mattress, mattress topper or pillow) on body cooling and night-time sleep. This systematic review with meta-analysis searched PubMed, ScienceDirect and Web of Science, from inception until March 4, 2024. We included randomized controlled trials aiming to investigate any type of bedding that induced body cooling compared to habitual sleep environment on sleep parameters in healthy adults. Two reviewers independently extracted data, appraised risk of bias by Cochrane tool, and estimated the mean differences between groups with 95% confidence interval. Meta-analyses and proportional meta-analyses were performed depending on the type of variable. The certainty of evidence was assessed using the Grades of Recommendation, Assessment, Development and Evaluation system. From 3454 articles screened, 9 studies met the inclusion criteria. Overall, with the certainty of the evidence ranging from very low to low we found no differences between groups on sleep onset latency, sleep efficiency, sleep proportion spent in each sleep stage (i.e. N1, N2, N3 and REM), wake after sleep onset, and total sleep time. Results could be interpreted with caution due to high heterogeneity in the estimated effects. With uncertainty of evidence, that ranged from very low to low, different bedding strategies had no effects on night-time sleep characteristics; however, the studies included into the qualitative synthesis suggested an effect of different bedding strategies on body cooling (i.e., lower core body temperature, p<0.05) from an acute perspective. Future studies on various forms of bedding interventions susceptible to favour and maintain sleep through a positive body thermal effect are highly warranted. CRD42021275369.

Does targeted temperature management at 33 °C improve outcome after cardiac arrest?

Following successful resuscitation from cardiac arrest, a complex set of pathophysiologic processes are acutely triggered, leading to substantial morbidity and mortality. Postarrest management remains a major challenge to critical care providers, with few proven therapeutic strategies to improve outcomes. One therapy that has received substantial focus is the intentional lowering of core body temperature for a discrete period of time following resuscitation. In this review, we will discuss the key trials and other evidence surrounding TTM and present opposing arguments, one 'against' the use of postarrest TTM and another 'for' the use of this therapeutic approach. Targeted temperature management, has been a topic of enormous controversy, as recently a number of clinical trials show conflicting results on the effect of TTM. Fundamental questions, about the dosing of TTM (e.g. use at 33 °C versus higher temperatures), or the use of TTM at all (as opposed to passive fever avoidance), remain active topics of global discussion. Systematic reviews on this topic also show variable results. There are several arguments for and against the use of TTM targeting 33 °C for alleviating brain injury after cardiac arrest. More studies are on the way that will hopefully provide more robust evidence and hopefully allow for consensus on this important topic.

Cool mama: Temperature regulation during high-intensity interval running in pregnant elite and recreational athletes

Background/ObjectiveRegular exercise during pregnancy is beneficial, but athletes often exceed the recommended 150 min of moderate-intensity activity, incorporate high-intensity exercises. The upper limit for exercise intensity and duration on fetal and maternal safety remains uncertain. A concern is a maternal core body temperature of >39.0 °C, potentially increase the risk of heat-related fetal malformations and complications during pregnancy. Blood flow redirection for thermoregulation could compromise fetal cardiovascular function, increasing the risk of miscarriage and preterm labor. This study evaluated whether pregnant women (gestational weeks 25–35) were at risk of exceeding a core body temperature of 39.0 °C during high-intensity running. We also investigated effects on skin temperature, fluid loss, and thermal sensation, comparing pregnant athletes to non-pregnant controls. MethodsIn this comparative cross-sectional study, 30 elite and recreational athletes (pregnant n = 15) completed up to five high-intensity treadmill-intervals. Core and skin temperature were continuously measured. Body weight was utilized to calculate the amount of fluid loss. ResultsHighest core body temperature were 38.76 °C and 39.56 °C in one pregnant and non-pregnant participant, respectively. Pregnant participants had lower core body temperatures (mean difference −0.47 °C, p ≤ 0.001) initially and a smaller increase (0.10 °C, p ≤ 0.003) during later intervals compared with the non-pregnant controls. Pregnant participants also showed a greater increase in skin temperature (4.08 ± 0.72 °C vs. 3.25 ± 0.86 °C, p = 0.008) and fluid loss (0.81 ± 0.19 L vs. 0.50 ± 0.12 L, p˂0.001). ConclusionPhysiological changes in pregnancy may enhance thermoregulation, indicating that high-intensity interval runs are unlikely to pose a risk of exceeding a core body temperature of 39 °C for pregnant athletes.

Peripartum Torpor: A Chilling Case Report and Review of the Literature

Purpose: To report a rare case of peripartum maternal hypothermia and bradycardia. Methods: Case report. Results: Torpor is a transient state of hibernation with hypothermia and bradycardia. Hypothermia is defined as an abnormally low core body temperature less than 36°C.1 Sinus bradycardia is defined as less than 60 beats/min. While occasionally hypothermia or bradycardia is seen in obstetric patients undergoing vaginal delivery, when combined together, it can be a rare, life-threatening state that requires prompt intervention to prevent adverse maternal and fetal outcomes. A 23 year-old G2P0102 at 33+3 weeks of gestation was admitted to the high risk obstetric service for preterm labor complicated by fetal growth restriction. She had a history of preeclampsia in a previous pregnancy, but otherwise denied any chronic medical problems. Upon arrival, her vital signs showed a temperature of 37°C, a pulse of 53 bpm, and blood pressure of 126/62 mmHg. Her white blood cell count was 12.4 x 109/L and hemoglobin was 11.3 g/dL. She received betamethasone for fetal lung maturity and penicillin for Group B streptococcus prophylaxis. As her cervix continued to dilate, she received an epidural for pain management. Once she was in active labor, she became bradycardic with a pulse in the 30s-40s bpm, as confirmed by EKG. She was completely asymptomatic at this time, and fetal heart tones were reassuring with a baseline between 110’s-130’s bpm. She delivered vaginally with 150 mL of estimated blood loss, and her bradycardia continued postpartum even after the epidural was discontinued. When she complained of feeling cold, multiple attempts with different oral and axillary thermometers could not obtain a reading. She was warmed with forced-air warming blankets, warmed blankets, and hot packs in her groin and axilla. During this time, discussion with the NICU staff revealed that her baby was also hypothermic at 33.3°C and hypoglycemic at 28 mg/dL at birth. Other than feeling cold, the patient continued to be asymptomatic despite hypotension and bradycardia. She appeared somnolent but was responsive to questions. Her uterus was firm with minimal vaginal bleeding and no purulent or foul-smelling vaginal discharge. Repeat laboratory testing revealed a white blood count of 19 x 109/L and lactate was 3.3 mmol/L. Her comprehensive metabolic panel was unremarkable. A chest x-ray was clear. A C-reactive protein was &lt; 0.3 mg/dL and sedimentation rate was 14 mm/h. A rectal continuous thermometer was placed, which eventually recorded a temperature at 33.3°C and upon recheck was 31.7°C. A multidisciplinary team, including Anesthesia, Internal Medicine, and Neurology, evaluated the patient due to concern for a central nervous system insult. She received fluid resuscitation and broad-spectrum antibiotics for sepsis protocol. Due to the concern for potential septic shock, the decision was made to transport her to the Medical ICU for further management. As she was leaving Labor &amp; Delivery, her temperature had increased to 36.9°C and her pulse to 61. Thyroid studies the next day revealed a normal Free T4 of 1.00 ng/dL and a high thyroid stimulating hormone level of 9.55 uIU/mL. However, despite an extensive workup, no clear etiology of her hypothermia and bradycardia was identified. Intervention with fluids and application of forced-air warming system resolved the hypothermia in less than 6 hours without relapse. Antibiotics were discontinued after one day due to low suspicion for systemic infection. She remained vitally stable and was discharged on postpartum day 2 without further complications. Conclusions: Maternal hypothermia is relatively common during cesarean delivery; however, very few cases report maternal hypothermia during vaginal delivery. An English language literature search for maternal hypothermia during vaginal delivery yielded less than 10 case reports – few of which identified a cause of the hypothermia – and none of which reported simultaneous maternal bradycardia. While our case is a very rare presentation and the etiology is still unknown, it highlights the importance of prompt recognition of vital sign derangements in peripartum patients as well as multidisciplinary attention.

96 Evaluating the impact of macroenvironment temperature on thermoregulatory and milk quality parameters in lactating sows and their litter

Abstract Farrowing facility macroenvironment temperatures (TMacro) are often maintained at the upper end of the thermoneutral zone (24–25°C) of lactating sows, which may result in heat stress and reduced milk quality and quantity. Therefore, the study objective was to evaluate the impact of TMacro on thermoregulatory and milk quality parameters in lactating sows and their litters. In two repetitions, 37 lactating sows (parity = 3.1 ± 1.7) and their litters (d 1 litter size = 12.0 ± 1.0) were housed within 1 of 3 farrowing rooms set to different TMacro: LOW (n = 12 sows and litters; 15.0 ± 0.4°C), MID (n = 13 sows and litters; 19.3 ± 0.2°C), and HIGH (n = 12 sows and litters; 24.6 ± 0.8°C). Lactating sows and litters were monitored from d 3 of lactation until weaning (19.8 ± 0.9 d of age). All litters were provided with a 0.34 × 1.52 m heating pad. Sow respiration rates (RR, breaths per minute, BPM) were measured daily at 0800, 1200, 1600 and 2000 h by counting the number of flank movements. Vaginal temperature (TV) was measured in all sows at 10-min intervals using implanted data loggers. One sentinel piglet from each litter was implanted with a temperature recording bolus at d 2 of age to monitor core body temperature in 15-min intervals. Milk samples were collected from all sows on d 6, 12, and 18 of lactation and analyzed for true protein %, total solid %, and fat %. Data were analyzed using PROC GLIMMIX. The litter was considered the experimental unit for piglet measures, and the sow was considered the experimental unit for sow measures. Respiration rates were greater (P &amp;lt; 0.01) for HIGH (48 ± 2 bpm) sows versus MID (33 ± 2 BPM) and LOW (27 ± 2 bpm) sows, but no differences were detected between MID and LOW sows. A TMacro treatment by lactation day effect was observed for TV (P = 0.02), where HOT sows had greater TV on lactation d 15 (+0.31°C), 18 (+0.43°C) and 19 (+0.34°C) versus MID and LOW sows. Piglet core body temperature was reduced (P &amp;lt; 0.01) in the HIGH (39.07 ± 0.06 °C) versus the MID (39.31 ± 0.06 °C) and LOW (39.33 ± 0.07 °C) treatment groups, but it was similar for MID and LOW litters. Fat % was reduced for COLD (6.15 ± 0.52%) versus MID (7.35 ± 0.50%) sows on d 12, but no differences were observed when compared with HIGH sows (6.97 ± 0.52%). In conclusion, the HIGH treatment resulted in physiological heat stress for lactating sows and lowered piglet core body temperature, but it had minimal effects on measures of milk quality.

Therapeutic Hypothermia Compared with Normothermia in Adults with Traumatic Brain Injury; Functional Outcome, Mortality, and Adverse Effects: A Systematic Review and Meta-Analysis.

The main focus of traumatic brain injury (TBI) management is prevention of secondary injury. Therapeutic hypothermia (TH), the induction of a targeted low core body temperature, has been explored as a potential neuroprotectant in TBI. The aim of this article is to synthesize the available clinical data comparing the use of TH with the use of normothermia in TBI. A systematic search was conducted through MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials for randomized clinical trials including one or more outcome of interest associated with TH use in TBI. Independent reviewers evaluated quality of the studies and extracted data on patients with TBI undergoing TH treatment compared with those undergoing normothermia treatment. Pooled estimates, confidence intervals (CIs), and risk ratios (RRs) or odds ratios were calculated for all outcomes. A total of 3,909 patients from 32 studies were eligible for analysis. Pooled analysis revealed a significant benefit of TH on mortality and functional outcome (RR 0.81, 95% CI 0.68-0.96, I2 = 41%; and RR 0.77; 95% CI 0.67-0.88, I2 = 68%, respectively). However, subgroup analysis based on risk of bias showed that only studies with a high risk of bias maintained this benefit. When divided by cooling method, reduced poor functional outcome was seen in the systemic surface cooling and cranial cooling groups (RR 0.68, 95% CI 0.59-0.79, I2 = 35%; and RR 0.44, 95% CI 0.29-0.67, I2 = 0%), and no difference was seen for the systemic intravenous or gastric cooling group. Reduced mortality was only seen in the systemic surface cooling group (RR 0.63, 95% CI 0.53-0.75, I2 = 0%,); however, this group had mostly high risk of bias studies. TH had an increased rate of pneumonia (RR 1.24, 95% CI 1.10-1.40, I2 = 32%), coagulation abnormalities (RR 1.63, 95% CI 1.09-2.44, I2 = 55%), and cardiac arrhythmias (RR 1.78, 95% CI 1.05-3.01, I2 = 21%). Once separated by low and high risk of bias, we saw no difference in these complications in the groups with low risk of bias. Overall quality of the evidence was moderate for mortality, functional outcome, and pneumonia and was low for coagulation abnormalities and cardiac arrhythmias. With the addition of several recent randomized clinical trials and a thorough quality assessment, we have provided an updated systematic review and meta-analysis that concludes that TH does not show any benefit over normothermia in terms of mortality and functional outcome.

Characterizing the impact of thermoregulation in patients after cardiac arrest: a retrospective cohort study.

Core body temperature has been extensively investigated as a thereuptic target in care after cardiac arrest. Nevertheless, the integrity of thermoregulation in patients after cardiac arrest has not been well studied. We sought to evaluate whether low spontaneous body temperature after cardiac arrest is associated with increased death and a worse neurologic outcome, and whether patients with low spontaneous body temperature exhibit features suggestive of impaired thermoregulation. We conducted a single-centre retrospective cohort study. We included all adult patients who underwent temperature control with hypothermia after cardiac arrest between 1 January 2014 and 30 June 2020. The primary exposure was low spontaneous core body temperature (< 35°C) at initiation of hypothermia therapy. The primary outcome was in-hospital death and the secondary outcome was poor neurologic outcomes at discharge. Five hundred and ninety-seven adult patients, comprising both in- and out-of-hospital cardiac arrests, were included. Patients with low spontaneous body temperature also had slightly lower average temperature, and more frequent transient but controlled breakthrough fever episodes in the first 24hr. In the multivariable logistic regression analysis, low spontaneous body temperature was associated with higher odds of in-hospital death (odds ratio, 2.9; 95% confidence interval, 1.9 to 4.2; P < 0.001). In this single-centre retrospective cohort study, low spontaneous core body temperature was associated with poor outcomes in patients after cardiac arrest. Patients with low spontaneous body temperature also exhibited features suggestive of impaired thermoregulation. Further research is needed to determine whether body temperature upon presentation reflects the robustness of the patient's underlying physiology and severity of brain insult after a cardiac arrest.

The Effect of Intraoperative Music on Sedation, Anxiety, and Hemodynamic Responses among Patients Undergoing Lower Segment Cesarean Section under Spinal Anesthesia

Background and Aim: Anxiety levels are high in spinal anesthesia as patients are awake. Sedation has an advantage that patients feel comfortable but if sedative drugs are not used judiciously, they can suppress the cardiovascular and respiratory system, lower core body temperature, or severely lower blood pressure. Music reduces awareness under anesthesia and has antianxiety effects. The effect of music on sedation using bispectral index (BIS) along with anxiety and hemodynamic parameters at different time intervals has been studied. Material and Methods: A hospital-based prospective randomized interventional study was done on 60 patients aged between 18 and 35 years undergoing lower segment cesarean sections. Two groups (music headphones with music and nonmusic headphones without music), each containing 30 subjects, were formed using a simple random technique by the sealed envelope method. The levels of sedation using BIS were measured preoperatively, after giving spinal anesthesia, then every 10 min till the end of surgery. Moreover, hemodynamic parameters were also monitored and recorded preoperatively and every 10 min till the end of surgery. Anxiety was measured using a visual analog score for anxiety preoperatively and postoperatively. Results: The BIS index was significantly lower in the music group compared to the nonmusic group from 20 min after start of surgery to the end of surgery (86.17 ± 4.48 vs. 75.73 ± 3.97, P &lt; 0.001). Anxiety was also significantly lower in the music group than in the nonmusic group (4.03 ± 1.47 vs. 0.50 ± 1.57, P &lt; 0.005). Heart rate (HR) was lower in the music group after 20 min of music therapy compared to the nonmusic group (87.87 ± 11.21 vs. 79.67 ± 6.67, P = 0.004) but there was no statistically significant difference in systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, and saturation of oxygen between two groups. Conclusion: Our data showed that intraoperative music listening under regional anesthesia has effect on sedation, anxiety, and physiological variables. Therefore, music therapy can be used as nonpharmacological intervention for reducing anxiety and sedation during surgery.

Abstract 145: Deploying Early Cooling at ICECAP Sites: A Barrier Assessment

Introduction: Best practices for implementing early temperature control in comatose survivors of cardiac arrest have yet to be defined. We surveyed sites enrolling in the Influence of Cooling Duration on Efficacy in Cardiac Arrest Patients (ICECAP) trial to understand variability in temperature control practices and identify barriers to rapid induction of cooling. Methods: A 23 question electronic survey was sent to principal investigators at 68 active ICECAP sites. Participants were queried on temperature control practices and asked to upload institutional protocols. Results: Fifty-two sites (76.5%) responded to the survey. While 45 sites (86.5%) had an institutional temperature control protocol, only 33 (63.5%) had an emergency department (ED)-specific protocol. Intravascular cooling was available at 21 sites (40.4%). The most frequent barriers to early initiation of temperature control were clinical skepticism regarding the importance of early cooling (n=32, 35.9%), insufficient nursing availability (n=18, 20.2%), lack of access to a cooling device in the ED (n=17, 19.1%), inability to achieve target temperature despite rapid connection to a cooling device (n=17, 19.1%), and delay due to procedures or intensive care unit transfer (n=5 5.6%). ED average boarding time exceeded two hours in 23 sites (44.2%). Fourteen (28%) sites did not have institutional protocols for early sedation or paralysis to help rapidly lower core body temperature during induction of temperature control. Paralytics were infrequently used during the induction phase; at the majority of sites (n=30, 61.2%) paralytics were used less than 20% of the time. Activation in the ICECAP trial resulted in quality improvements to institutional cooling protocols (n=14, 26.9%), such as purchase of cooling devices for the ED, development of sedation or paralytic protocols, and educational initiatives to shorten the time to target temperature. Conclusion: Many of the identified barriers for rapid initiation of temperature control are modifiable. Nursing and provider education regarding the importance of early cooling and development of standardized sedation and paralytic protocols may be effective strategies to improve early cooling practices.

Heat Stress Mitigation: Impact of Increased Cooling Sessions on Milk Yield and Welfare of Dairy Buffaloes in a Semiarid Summer.

The current study aimed to evaluate the impact of increasing cooling sessions from three to five times a day on milk yield and the welfare of dairy buffaloes during a semiarid summer in Pakistan. Eighteen Nili Ravi buffaloes were randomly assigned to three cooling strategies: (1) CTL, where buffaloes were cooled with a handheld hosepipe twice daily for 5 min each; (2) 3CS, where buffaloes were cooled using sprinklers three times daily; and (3) 5CS, where buffaloes were cooled using sprinklers five times daily. Each sprinkler cooling session lasted 1 h, with a 6 min cycle of 3 min of water on and 3 min off. Results showed that the 5CS group produced 1.6 and 3.2 kg more milk per day compared to the 3CS and CTL groups, respectively (p < 0.001). Both the 5CS and 3CS groups had consistently lower core body temperatures and respiration rates than the CTL group. Buffaloes in the 5CS group spent significantly more time eating (p < 0.001). Additionally, the 5CS group exhibited lower cortisol and blood urea nitrogen levels (p = 0.001) and higher glucose levels than the CTL group (p = 0.006). In conclusion, increasing cooling sessions to five times daily improved milk yield and welfare compared to the traditional cooling strategy (CTL) in dairy buffaloes during semiarid summers, highlighting the benefits of optimized cooling practices.

Impact of intraoperative blood products, fluid administration, and persistent hypothermia on bleeding leading to reexploration after cardiac surgery

ObjectiveRisk factors for severe postoperative bleeding after cardiac surgery remain multiple and incompletely elucidated. We evaluated the impact of intraoperative blood product transfusions, intravenous fluid administration, and persistently low core body temperature (CBT) at intensive care unit arrival on risk of perioperative bleeding leading to reexploration. MethodsWe retrospectively queried our tertiary care center's Society of Thoracic Surgeons Institutional Database for all index, on-pump, adult cardiac surgery patients between July 2016 and September 2022. Intraoperative fluid (crystalloid and colloid) and blood product administrations, as well as perioperative CBT data, were harvested from electronic medical records. Linear and nonlinear mixed models, treating surgeon as a random effect to account for inter-surgeon practice differences, were used to assess the association between above factors and reexploration for bleeding. ResultsOf 4037 patients, 151 (3.7%) underwent reexploration for bleeding. Reexplored patients experienced remarkably greater postoperative morbidity (23% vs 6%, P < .001) and 30-day mortality (14% vs 2%, P < .001). In linear models, progressively increasing IV crystalloid administration (adjusted odds ratio, 1.11, 95% confidence interval, 1.03-1.19) and decreasing CBT on intensive care unit arrival (adjusted odds ratio, 1.20; 95% confidence interval, 1.05-1.37) were associated with greater risk of bleeding leading to reexploration. Nonlinear analysis revealed increasing risk after ∼6 L of crystalloid administration and a U-shaped relationship between CBT and reexploration risk. Intraoperative blood product transfusion of any kind was not associated with reexploration. ConclusionsWe found evidence of both dilution- and hypothermia-related effects associated with perioperative bleeding leading to reexploration in cardiac surgery. Interventions targeting modification of such risk factors may decrease the rate this complication.

Association of Phenotypic Markers of Heat Tolerance with Australian Genomic Estimated Breeding Values and Dairy Cattle Selection Indices.

Dairy cattle predicted by genomic breeding values to be heat tolerant are known to have less milk production decline and lower core body temperature increases in response to elevated temperatures. In a study conducted at the University of Melbourne's Dookie Robotic Dairy Farm during summer, we identified the 20 most heat-susceptible and heat-tolerant cows in a herd of 150 Holstein Friesian lactating cows based on their phenotypic responses (changes in respiration rate, surface body temperature, panting score, and milk production). Hair samples were collected from the tip of the cows' tails following standard genotyping protocols. The results indicated variation in feed saved and HT genomic estimated breeding values (GEBVs) (p ≤ 0.05) across age, indicating a potential for their selection. As expected, the thermotolerant group had higher GEBVs for HT and feed saved but lower values for milk production. In general, younger cows had superior GEBVs for the Balanced Performance Index (BPI) and Australian Selection Index (ASI), whilst older cows were superior in fertility, feed saved (FS), and HT. This study demonstrated highly significant (p ≤ 0.001) negative correlations (-0.28 to -0.74) between HT and GEBVs for current Australian dairy cattle selection indices (BPI, ASI, HWI) and significant (p ≤ 0.05) positive correlations between HT and GEBVs for traits like FS (0.45) and fertility (0.25). Genomic selection for HT will help improve cow efficiency and sustainability of dairy production under hot summer conditions. However, a more extensive study involving more lactating cows across multiple farms is recommended to confirm the associations between the phenotypic predictors of HT and GEBVs.

Targeted temperature management in brain edema

Background: Targeted temperature management is a treatment strategy to lower core body temperature to achieve neuroprotection or reduce elevated intracranial pressure. Therefore, it has been increasingly used in the neurointensive care unit to manage various types of acute neurologic injuries.Current Concepts: Targeted temperature management can be divided into three distinct phases, including induction, maintenance, and rewarming, and each phase has risks and predictable complications. In patients with acute neurocritical illnesses, including traumatic brain injury, subarachnoid hemorrhage, intracranial hemorrhage, and ischemic stroke, brain edema is a potentially life-threatening complication as it raises the intracranial pressure, leading to brain herniation and permanent neurological damage. In this sense, targeted temperature management can be considered the final strategy for medical treatment for controlling an intracranial pressure crisis in patients with severe brain injury.Discussion and Conclusion: In the neurointensive care unit, applying targeted temperature management to patients with severe brain injuries may be challenging. Targeted temperature management in critically ill neurological patients is associated with an increased risk of systemic complications, as hypothermia is prolonged, requiring a comprehensive patient-by-patient assessment of the advantages and disadvantages of treatment. Except for cerebral pressure management, analyses of targeted temperature management in patients with traumatic brain injury and subarachnoid hemorrhage remain controversial regarding its effect on prognosis. Targeted temperature management should be reserved for selective patients, and further studies are needed to improve the efficacy of hypothermia for individual conditions, including intracerebral hemorrhage and ischemic stroke.

Cardiac Rhythms and Variation in Hibernating Arctic Ground Squirrels.

AbstractThe dramatic decrease in heart rate (HR) during entrance into hibernation is not a mere response to the lowering of core body temperature (Tb) but a highly regulated fall, as the decrease in HR precedes the drop in Tb. This regulated fall in HR is thought to be mediated by increased cardiac parasympathetic activity. Conversely, the sympathetic nervous system is thought to drive the increase of HR during arousal. Despite this general understanding, we lack temporal information on cardiac parasympathetic regulation throughout a complete hibernation bout. The goal of this study was to fill this gap in knowledge by using Arctic ground squirrels implanted with electrocardiogram/temperature telemetry transmitters. Short-term HR variability (root mean square of successive differences [RMSSD]), an indirect measure of cardiac parasympathetic regulation, was calculated in 11 Arctic ground squirrels. RMSSD, normalized as RMSSD/RR interval (RRI), increased fourfold during early entrance (from to , ). RMSSD/RRI peaked after HR dropped by over 90% and Tb fell by 70%. Late entrance was delineated by a decline in RMSSD/RRI while Tb continued to decrease. During arousal, HR started to increase 2 h before Tb, with a concurrent decrease in RMSSD/RRI to a new minimum. As Tb increased to a maximum during interbout arousal, HR declined, and RMSSD/RRI increased. These data suggest that activation of the parasympathetic nervous system initiates and regulates the HR decrease during entrance into hibernation and that withdrawal of parasympathetic activation initiates arousal. We conclude that cardiac parasympathetic regulation persists throughout all phases of a hibernation bout-a feature of the autonomic nervous system's regulation of hibernation that was not appreciated previously.

An Overview of Exertional Heat Illness in Thoroughbred Racehorses: Pathophysiology, Diagnosis, and Treatment Rationale.

Exertional heat illness (EHI) is a complex medical disease. The thoroughbred (TB) racehorse is at considerable risk because of the intensity of its exercise activity and its high rate of metabolic heat production. The pathophysiology of EHI can combine aspects of both the heat toxicity pathway and the heat sepsis or endotoxemic pathway. Treatment regimes depend upon the detection of earliest clinical signs, rapid assessment, aggressive cooling and judicious use of ancillary medications. Ice-cold water provides the most rapid cooling, consistent with the need to lower core body temperature before tissue damage occurs. Research into EHI/HS by inducing the condition experimentally is ethically unjustifiable. Consequently, leading researchers in the human field have conceded that "most of our knowledge has been gained from anecdotal incidents, gathered from military personnel and athletes who have collapsed during or following physical activity, and that retrospective and case studies have provided important evidence regarding recognition and treatment of EHI". The authors' review into EHI shares that perspective, and the recommendations made herein are based on observations of heat-affected racehorses at the racetrack and their response, or lack of response, to treatment. From 2014 to 2018, 73 race meetings were attended, and of the 4809 individual starters, signs of EHI were recorded in 457. That observational study formed the basis for a series of articles which have been published under the title, 'EHI in Thoroughbred racehorses in eastern Australia', and forms the background for this review.

Stress Drivers of Glucose Dynamics during Ozone Exposure Measured Using Radiotelemetry in Rats.

Inhaled irritant air pollutants may trigger stress-related metabolic dysfunction associated with altered circulating adrenal-derived hormones. We used implantable telemetry in rats to assess real-time changes in circulating glucose during and after exposure to ozone and mechanistically linked responses to neuroendocrine stress hormones. First, using a cross-over design, we monitored glucose during ozone exposures (0.0, 0.2, 0.4, and ) and nonexposure periods in male Wistar Kyoto rats implanted with glucose telemeters. A second cohort of unimplanted rats was exposed to ozone (0.0, 0.4 or 0.8 ppm) for 30 min, 1 h, 2 h, or 4 h with hormones measured immediately post exposure. We assessed glucose metabolism in sham and adrenalectomized rats, with or without supplementation of adrenergic/glucocorticoid receptor agonists, and in a separate cohort, antagonists. Ozone () was associated with significantly higher blood glucose and lower core body temperature beginning 90 min into exposure, with reversal of effects 4-6 h post exposure. Glucose monitoring during four daily 4-h ozone exposures revealed duration of glucose increases, adaptation, and diurnal variations. Ozone-induced glucose changes were preceded by higher levels of adrenocorticotropic hormone, corticosterone, and epinephrine but lower levels of thyroid-stimulating hormone, prolactin, and luteinizing hormones. Higher glucose and glucose intolerance were inhibited in rats that were adrenalectomized or treated with adrenergic plus glucocorticoid receptor antagonists but exacerbated by agonists. We demonstrated the temporality of neuroendocrine-stress-mediated biological sequalae responsible for ozone-induced glucose metabolic dysfunction and mechanism in a rodent model. Stress hormones assessment with real-time glucose monitoring may be useful in identifying interactions among irritant pollutants and stress-related illnesses. https://doi.org/10.1289/EHP11088.

The circadian variation of sleep and alertness of postmenopausal women.

Several factors may contribute to the high prevalence of sleep disturbances occurring in postmenopausal women. However, the contribution of the circadian timing system to their sleep disturbances remains unclear. In the present study, we aim to understand the impact of circadian factors on changes of sleep and alertness occurring after menopause. Eight healthy postmenopausal women and 12 healthy young women in their mid-follicular phase participated in an ultradian sleep-wake cycle procedure (USW). This protocol consisted of alternating 60-min wake periods and nap opportunities for ≥ 48 h in controlled laboratory conditions. Core body temperature (CBT), salivary melatonin, self-reported alertness, and polysomnographically recorded sleep were measured across this procedure. In both groups, all measures displayed a circadian variation throughout the USW procedure. Compared to young women, postmenopausal women presented lower CBT values, more stage N1 and N2 sleep, and number of arousals. They also showed a reduced amplitude of the circadian variation of melatonin, total sleep time (TST), sleep onset latency (SOL), stage N3 sleep, and alertness levels. Postmenopausal women fell asleep faster and slept more during the biological day and presented higher alertness levels during the biological night than young women. These results support the hypothesis of a weakened circadian signal promoting sleep and wakefulness in older women. Aging processes including hormonal changes may be main contributors to the increased sleep-wake disturbances after menopause.

Improving Genomic Selection for Heat Tolerance in Dairy Cattle: Current Opportunities and Future Directions.

Heat tolerance is the ability of an animal to maintain production and reproduction levels under hot and humid conditions and is now a trait of economic relevance in dairy systems worldwide because of an escalating warming climate. The Australian dairy population is one of the excellent study models for enhancing our understanding of the biology of heat tolerance because they are predominantly kept outdoors on pastures where they experience direct effects of weather elements (e.g., solar radiation). In this article, we focus on evidence from recent studies in Australia that leveraged large a dataset [∼40,000 animals with phenotypes and 15 million whole-genome sequence variants] to elucidate the genetic basis of thermal stress as a critical part of the strategy to breed cattle adapted to warmer environments. Genotype-by-environment interaction (i.e., G × E) due to temperature and humidity variation is increasing, meaning animals are becoming less adapted (i.e., more sensitive) to changing environments. There are opportunities to reverse this trend and accelerate adaptation to warming climate by 1) selecting robust or heat-resilient animals and 2) including resilience indicators in breeding goals. Candidate causal variants related to the nervous system and metabolic functions are relevant for heat tolerance and, therefore, key for improving this trait. This could include adding these variants in the custom SNP panels used for routine genomic evaluations or as the basis to design specific agonist or antagonist compounds for lowering core body temperature under heat stress conditions. Indeed, it was encouraging to see that adding prioritized functionally relevant variants into the 50k SNP panel (i.e., the industry panel used for genomic evaluation in Australia) increased the prediction accuracy of heat tolerance by up to 10% units. This gain in accuracy is critical because genetic improvement has a linear relationship with prediction accuracy. Overall, while this article used data mainly from Australia, this could benefit other countries that aim to develop breeding values for heat tolerance, considering that the warming climate is becoming a topical issue worldwide.

Does Radial Artery Cannulation Affect the Perfusion of the Dominant Hand in Adult Patients with Normal Modified Allen's Test Undergoing Cardiac Surgeries? Data Derived from the Peripheral Perfusion Index

This study aimed to evaluate the effect of radial artery cannulation on hand perfusion in patients with normal modified Allen's test undergoing cardiac surgeries using cardiopulmonary bypass (CPB). Prospective follow-up study. Single institution, Assiut University Cardiothoracic Hospital. Forty-nine patients who underwent cardiac surgeries using cardiopulmonary bypass were enrolled. Cannulation of radial artery in the dominant hand using a 20-gauge catheter. The primary outcomes were the mean peripheral perfusion index (PPI) >60 seconds (mean PPI60) and the thumb temperature, which were measured at different times before and during the surgery. There was a statistically significant difference in the mean PPI60 between both hands (p=0.033). Before skin incision, the mean PPI60 was significantly higher in the noncannulated hand (p < 0.001). Also, there was a statistically significant difference in the thumb temperature between both hands (p=0.013). At low core body temperature, the thumb temperature was significantly lower in the noncannulated hand (p=0.017). In adult patients undergoing cardiac surgeries using CPB, even with normal modified Allen's test, radial artery cannulation may affect the perfusion of the dominant hand, especially at low arterial blood pressure or low core body temperature. Since the PPI is one of the noninvasive methods used for intraoperative assessment of the peripheral perfusion, the authors recommend the use of the noncannulated hand for this purpose to not misguide this assessment.